Investigation of kerf taper angle and surface roughness in abrasive water jet machined glass fiber-reinforced polyester composites

Glass fiber-reinforced polymer (GFRP) composites are commonly used in aerospace, automotive, and structural applications due to their excellent strength-to-weight ratio and resistance to corrosion. Conventional machining methods, however, still face persistent difficulties in maintaining dimensional accuracy and producing smooth surface finishes. Abrasive Water Jet Machining (AWJM) offers a non-traditional alternative with improved performance, though limited studies address its effects across varying material thicknesses. This study investigates the influence of AWJM parameters, water pressure (250–350 MPa), traverse speed (1500–2500 mm/min), and stand-off distance (2–4 mm) on kerf taper angle and surface roughness in 3 mm and 6 mm thick GFRP laminates. The composites were fabricated using hand lay-up and compression molding. Experiments were designed using an L9 Taguchi orthogonal array with signal-to-noise (S/N) ratio analysis under the “Smaller is Better” criterion. Results showed that stand-off distance contributed the most to kerf taper (54.26% for 3 mm) and surface roughness (80.25% for 3 mm), while water pressure dominated in thicker laminates (56.63% for 6 mm taper, 22.79% for roughness). The optimal combination of 350 MPa water pressure, 1500 mm/min traverse speed, and 2 mm stand-off distance achieved a minimum kerf taper of 1.05° and surface roughness of 2.0 µm in 3 mm laminates, compared to 1.20° and 2.3 µm in 6 mm laminates. These findings provide a quantitative basis for optimizing AWJM parameters to improve machining quality in GFRP components for lightweight engineering applications.